1. Field of the Invention
This invention relates to an aircraft transparency and more particularly to an aircraft transparency having vibration dampening/sound absorbing properties, optionally heating properties, and to the method of making the same.
2. Discussion of the Presently Available Technology
The transmission of unwanted sound/vibrations through an aircraft transparency and into the aircraft, in particular the aircraft cabin, is undesirable, and may cause discomfort to the cabin's occupants. Efforts have been made to reduce the transmission of sound/vibrations through aircraft transparencies. Such efforts have been generally directed to transparencies having several panes (e.g. four or more panes) maintained in spaced-apart relationship within a spacer-frame assembly, which spacer frame assembly is affixed to a corresponding opening in the body of the aircraft. The spaced panes provide-a plurality of airspaces therebetween, which, among other things, reduce or eliminate the transmission of external sound/vibrations through the transparency into the cabin.
While generally effective, such transparencies are costly and time consuming to manufacture. Further, such transparencies are heavy due to the fact that they require several panes, and as may be appreciated by those skilled in the art of aircraft manufacture, increased weight in aircraft components is undesirable because, among other reasons, it adds expense to the operation of the aircraft.
In the automotive industry, there have been efforts to improve the comfort of automobile passengers by reducing transmission of unwanted noise through the automobile's glass surfaces into the passenger compartment. Unlike the aircraft industry, such efforts in the automotive industry have generally not relied upon a plurality of spaced-apart panes to obtain the desired reduction in noise transmission. Rather, these efforts have been largely directed toward the windshield, which is generally a laminate of two glass sheets with one or more interlayers therebetween. Efforts to produce acoustically insulating windshields have generally been directed to identifying interlayer materials or combinations of interlayer materials to provide the windshield with the desired sound absorbing properties. Examples include U.S. patent application Ser. No. 08/783,596 to Benson et al., filed Jan. 1, 1997, hereby incorporated herein by reference, (hereinafter "Benson", European Patent Application Nos. EP 0 566 890 A1, and EP 0 763 420 A1, all of which describe laminated automotive glazing for acoustic insulation.
As can be appreciated by those skilled in the art, it would be advantageous to provide aircraft transparencies which reduce or eliminate the transmission of sound and/or vibrations through the transparency which eliminate the limitations of the presently available transparencies.